Methods of forming power electronic assemblies using metal inverse opal structures and encapsulated-polymer spheres

ABSTRACT

A method of forming a bonding assembly that includes positioning a plurality of polymer spheres against an opal structure and placing a substrate against a second major surface of the opal structure. The opal structure includes the first major surface and the second major surface with a plurality of voids defined therebetween. The plurality of polymer spheres encapsulates a solder material disposed therein and contacts the first major surface of the opal structure. The method includes depositing a material within the voids of the opal structure and removing the opal structure to form an inverse opal structure between the first and second major surfaces. The method further includes removing the plurality of polymer spheres to expose the solder material encapsulated therein and placing a semiconductor device onto the inverse opal structure in contact with the solder material.

BACKGROUND Field

The present specification generally relates to power electronicsassemblies, and more particularly, to methods of forming powerelectronics assemblies with bonding layers that include encapsulatedbonding spheres therein that provide electrical contact betweenelectrodes, cooling of semiconductor devices, and thermal stresscompensation.

Technical Background

As power electronics devices are designed to operate at increased powerlevels, thereby generating more heat due to the demands of electricalsystems, conventional heat sinks are unable to adequately removesufficient heat to effectively lower the operating temperature of thepower electronics devices to acceptable temperature levels. Further,conventional heat sinks and cooling structures require additionalbonding layers and thermal matching materials (e.g., bond layers,substrates, thermal interface materials). These additional layers addsubstantial thermal resistance to the overall assembly and make thermalmanagement of the electronics system challenging.

Metal inverse opal (MIO) structures provide a thermal management of theassembly due to a general porosity of the structure, which enablesenhanced nucleation sites for receiving a cooling fluid therein.However, due to the multiple pores (i.e., voids) present within the MIOstructure, bonding the components of the power electronics assembly tothe MIO structure may be challenging.

SUMMARY

In one embodiment, a method of forming a bonding assembly includespositioning a plurality of polymer spheres against an opal structure,wherein the opal structure includes a first major surface and a secondmajor surface with a plurality of voids defined therebetween. Theplurality of polymer spheres encapsulates a solder material disposedtherein and contacts the first major surface of the opal structure. Themethod further includes placing a substrate against the second majorsurface of the opal structure, depositing a material within the voids ofthe opal structure, and removing the opal structure to form an inverseopal structure between the first and second major surfaces. The methodfurther includes removing the plurality of polymer spheres to expose thesolder material encapsulated therein and placing a semiconductor deviceonto the inverse opal structure in contact with the solder material.

In another embodiment, a method of forming a power electronic assemblyincludes attaching a metal substrate to a first surface of an opalstructure, the opal structure including a plurality of voids definedbetween the first surface and a second surface. The method furtherincludes attaching a plurality of polymer spheres to the second surfaceof the opal structure, the plurality of polymer spheres encapsulating asolder material disposed therein, and forming an inverse opal structurebetween the metal substrate and the plurality of polymer spheres byremoving the opal structure disposed therebetween. The method furtherincludes exposing the solder material from within the plurality ofpolymer spheres by removing the plurality of polymer spheres andsecuring a non-metal substrate against the inverse opal structure and incontact with the solder material.

In yet another embodiment, a method for bonding a semiconductor deviceto a substrate using metal inverse opals, the method includingdepositing the substrate onto a first major surface of an opalstructure, wherein the opal structure defines a plurality of voidsbetween the first major surface and a second major surface of the opalstructure. The method further includes receiving a plurality of polymerspheres within at least one of the plurality of voids of the opalstructure, electrodepositing metal within the plurality of voids of theopal structure to bond the substrate to the opal structure, anddissolving the opal structure to provide a metal inverse opal structuresecured along the substrate, the metal inverse opal structure defining aplurality of spheres. The method further includes dissolving theplurality of polymer spheres from within the metal inverse opalstructure to expose an encapsulated material positioned within theplurality of polymer spheres and depositing the semiconductor deviceonto the metal inverse opal structure to bond the substrate to thesemiconductor device.

These and additional features provided by the embodiments describedherein will be more fully understood in view of the following detaileddescription, in conjunction with the drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

The embodiments set forth in the drawings are illustrative and exemplaryin nature and not intended to limit the subject matter defined by theclaims. The following detailed description of the illustrativeembodiments can be understood when read in conjunction with thefollowing drawings, wherein like structure is indicated with likereference numerals and in which:

FIG. 1 schematically depicts an illustrative cross-sectional side viewof an assembly having a metal substrate thermally bonded to a devicesubstrate with a metal inverse opal structure disposed therebetweenaccording to one or more embodiments shown and described herein;

FIG. 2A schematically depicts a method of fabricating the assembly ofFIG. 1 by positioning an opal structure against a plurality of polymerspheres according to one or more embodiments shown and described herein;

FIG. 2B schematically depicts a method of fabricating the assembly ofFIG. 1 by positioning a metal substrate against the opal structureaccording to one or more embodiments shown and described herein;

FIG. 2C schematically depicts a method of fabricating the assembly ofFIG. 1 by depositing a metal within the opal structure and dissolvingthe opal structure and the plurality of polymer spheres to form a metalinverse opal structure with a solder material exposed along a surface ofthe metal inverse opal structure according to one or more embodimentsshown and described herein;

FIG. 2D schematically depicts a method of fabricating the assembly ofFIG. 1 by positioning a device substrate against the surface of themetal inverse opal structure including the solder material according toone or more embodiments shown and described herein;

FIG. 2E schematically depicts a method of fabricating the assembly ofFIG. 1 by melting the solder material according to one or moreembodiments shown and described herein;

FIG. 3 depicts a flow diagram of an illustrative method of forming theassembly of FIG. 1 according to one or more embodiments shown anddescribed herein.

FIG. 4A schematically depicts an illustrative perspective view ofanother assembly having a metal substrate deposited onto a devicesubstrate with an opal structure disposed therebetween according to oneor more embodiments shown and described herein;

FIG. 4B schematically depicts the assembly of FIG. 4A with the opalstructure dissolved to form a metal inverse opal structure with a solderpaste extending about an outer lateral surface of the metal inverse opalstructure according to one or more embodiments shown and describedherein;

FIG. 5 depicts a flow diagram of an illustrative method of forming theassembly of FIGS. 4A-4B according to one or more embodiments shown anddescribed herein;

FIG. 6A schematically depicts an illustrative cross-sectional side viewof yet another assembly having a metal substrate thermally bonded to adevice substrate with a metal inverse opal structure disposedtherebetween and including a plurality of polymer spheres thereinaccording to one or more embodiments shown and described herein; and

FIG. 6B schematically depicts the assembly of FIG. 6A with the pluralityof polymer spheres dissolved to form a plurality of solder spheresdisposed within the metal inverse opal structure according to one ormore embodiments shown and described herein;

FIG. 7 depicts a flow diagram of an illustrative method of forming theassembly of FIGS. 6A-6B according to one or more embodiments shown anddescribed herein.

DETAILED DESCRIPTION

Power electronics devices are often utilized in high-power electricalapplications, such as inverter systems for hybrid electric vehicles andelectric vehicles. Such power electronics devices include powersemiconductor devices such as power insulated-gate bipolar transistors(IGBTs) and power transistors thermally bonded to a metal substrate.With advances in battery technology and increases in electronics devicepackaging density, operating temperatures of power electronics deviceshave increased and can exceed about 200° Celsius. Heat sink devices orother similar thermal transfer devices may be coupled to the powerelectronics devices to remove heat and lower the maximum operatingtemperature of a power semiconductor device. For example, cooling fluidmay be used to receive heat generated by the power semiconductor deviceby convective thermal transfer, and remove such heat from the powersemiconductor device.

It should be understood that the substrates (e.g., power semiconductordevices) and assemblies (e.g., power electronics assemblies) describedherein may be incorporated into an inverter circuit or system thatconverts direct current electrical power into alternating currentelectrical power and vice versa depending on the particular application.For example, in a hybrid electric vehicle application (not shown),several power electronics assemblies may be electrically coupledtogether to form a drive circuit that converts direct current electricalpower provided by a bank of batteries into alternating electrical powerthat is used to drive an electric motor coupled to the wheels of avehicle to propel the vehicle using electric power. The powerelectronics assemblies used in the drive circuit may also be used toconvert alternating current electrical power resulting from use of theelectric motor and regenerative braking back into direct currentelectrical power for storage in the bank of batteries.

Power semiconductor devices may generate a significant amount of heatduring operation, which require bonds between the semiconductor deviceand the metal substrate that can withstand higher temperatures andthermally-induced stresses due to CTE mismatch. The MIO bondingstructures described and illustrated herein may compensate for thethermally-induced stresses generated during thermal bonding of thesemiconductor devices to the metal substrate by manageably controllingthe thermal expansion and/or stiffness experienced by the layers of themetal substrate and semiconductor devices while also providing a compactpackage design. The MIO bonding structure may also provide anelectrically conductive path between the semiconductor device and thesubstrate, and in some embodiments, a pair of electrodes disposed alongthe semiconductor device and the substrate. The MIO bonding structuremay further provide a cooling layer for cooling the semiconductordevices during operation of the power electronics devices.

The present disclosure relates generally to a simplified method forforming the power electronic devices described above including a powersemiconductor device bonded to a metal substrate with a MIO bondingstructure disposed therebetween. One non-limiting example of a methodfor forming an assembly (e.g., a power electronics assembly) includespositioning a plurality of polymer spheres against an opal structurealong a first major surface thereof and positioning a substrate againstthe opal structure along a second major surface thereof. A material,such as a metal (e.g., copper), may be deposited onto the opal structuresuch that the metal is received through a plurality of voids of the opalstructure. In this instance, removing the opal structure, for example,by dissolving the opal structure, forms a metal inverse opal (MIO)bonding structure secured against the substrate and the plurality ofpolymer spheres. Removing the plurality of polymer spheres exposes asolder material disposed within the plurality of polymer spheres.

With the MIO bonding structure formed against the substrate and with thesolder material exposed along the first major surface of the MIO bondingstructure, a semiconductor device may be positioned on the MIO bondingstructure along the first major surface thereof opposite of thesubstrate located along the second major surface thereof. Accordingly,the semiconductor device is positioned in contact with or adjacent tothe solder material. The semiconductor device may be bonded to the MIObonding structure and the substrate, for example, by heating theassembly and melting the solder material to secure the semiconductordevice to the MIO bonding structure, thereby forming the assembly.

The MIO bonding structure may serve as an electrically conductive layerbetween the substrate and the semiconductor device such that thesubstrate may be in electrical communication with the semiconductordevice through the porous MIO bonding structure. The MIO bondingstructure includes a porous structure defining a series ofinterconnected voids extending therethrough. Additionally, the MIObonding structure may provide a thermally conductive cooling layer forthe assembly such that a cooling fluid may enter the assembly and flowthrough the porous structure of the MIO bonding structure, and inparticular through the interconnected voids defined within the MIObonding structure, to cool the substrate and/or the semiconductordevice. The MIO bonding structure may provide a thermal stresscompensation layer to the bonding assembly and may be incorporated intoinverter systems of electrified vehicles described herein to reducethermally-induced stresses due to CTE mismatch without the need foradditional interface layers. Various embodiments of opal structures,polymer spheres, MIO bonding structures and bonding assemblies will bedescribed in greater detail herein.

Referring initially to FIG. 1, a non-limiting example of an assembly100, such as, for example, a power electronics assembly, is illustrated.The example assembly 100 generally includes a semiconductor device 110with a top surface 112 and a bottom surface 114, and a substrate 120with a top surface 122 and a bottom surface 124. An inverse opal bondingstructure 130 (e.g., metal inverse opal bonding structure) with a firstmajor surface 132 and a second major surface 134 is positioned betweenand bonded to the semiconductor device 110 and the substrate 120. Inparticular, the top surface 122 of the substrate 120 is bonded to theMIO bonding structure 130 along the second major surface 134, and thebottom surface 114 of the semiconductor device 110 is bonded to the MIObonding structure 130 along the first major surface 132. As will bedescribed in greater detail herein, the MIO bonding structure 130 may beformed and bonded to the semiconductor device 110 by depositing aplurality of polymer spheres 150 along the first major surface 132 ofthe MIO bonding structure 130 (FIG. 2A) such that the semiconductordevice 110 is in contact with and/or positioned adjacent to theplurality of polymer spheres 150 (FIG. 2D) when bonded thereto. In otherembodiments, the plurality of polymer spheres 150 may be depositedwithin the MIO bonding structure 130 and/or about an exterior of the MIObonding structure 130. The MIO bonding structure 130 may be formed andbonded to the substrate 120 by depositing a metal (e.g., copper) alongan opal structure 140 (FIGS. 2A-2B) that is positioned against thesubstrate 120 prior to attachment of the semiconductor device onto theassembly 100.

Still referring to FIG. 1, the semiconductor device 110 may generally beany electronic device that uses semiconductor materials. In someembodiments, the semiconductor device 110 may be formed from a wide bandgap semiconductor material suitable for the manufacture or production ofpower semiconductor devices, such as, for example, a powerinsulated-gate bi-polar transistor (IGBTs), a power metal-oxidefield-effect transistor (MOSFET), a power transistor, and the like. Insome embodiments, the semiconductor device 110 may be formed from wideband gap semiconductor materials. Non-limiting examples of such wideband gap semiconductor materials include silicon carbide (SiC), aluminumnitride (AlN), gallium nitride (GaN), gallium oxide (Ga₂O₃), boronnitride (BN), diamond, and/or the like.

The substrate 120 serves as a bottom substrate for the assembly 100 andmay be formed of any type of material, particularly those that are usedfor power semiconductor device assemblies. Non-limiting examples includemetal substrates, e.g., substrates formed from copper (Cu), e.g., oxygenfree Cu, aluminum (Al), Cu alloys, Al alloys, and the like, directbonded copper substrates or semiconductor (e.g., silicon) substrates. Inembodiments, the substrate 120 may be plated with a metal on an exteriorsurface, such as, for example, aluminum (Al), nickel (N), and the like.As will be described in greater detail herein, the substrate 120 may beformed from a thermally conductive material such that heat from thesemiconductor device 110 is transferred to the substrate 120 via the MIObonding structure 130 interlaid between the semiconductor device 110 andthe substrate 120.

The thickness of the semiconductor device 110 and the substrate 120 maydepend on the intended use of the assembly 100. In non-limitingexamples, the semiconductor device 110 has a thickness of about 0.1millimeters to about 0.3 millimeters, and the substrate 120 has athickness of about 1.0 millimeter to about 2.0 millimeters. In thisinstance, the assembly 100 may have a maximum height of about 1.1millimeters to about 2.3 millimeters. It should be understood that otherthicknesses of the semiconductor device 110 and/or the substrate 120 maybe utilized in assembly 100 without departing from the scope of thepresent disclosure.

The MIO bonding structure 130 may generally be any inverse opalstructure, such as, for example, a copper inverse opal (CIO) structure,a nickel inverse opal (NIO) structure, and/or the like. The MIO bondingstructure 130 has a plurality of pores 136 that define a porosity of theMIO bonding structure 130. The plurality of pores 136 may facilitate athermal conductivity for the MIO bonding structure 130 between thesemiconductor device 110 and the substrate 120. In particular, theplurality of pores 136 define a plurality of dimples 138 (or othersimilar depressions or indentations) such that fluid introduced into theassembly 100 can flow through each of the plurality of networked pores136 throughout the MIO bonding structure 130 and contact a greateramount of surface area for the purposes of heat transfer. Such fluid mayinclude a cooling fluid received through the plurality of pores 136 andtransferred through the MIO bonding structure 130 to contact the bottomsurface 114 of the semiconductor device 110 and the top surface 122 ofthe substrate 120 to transfer heat generated by the semiconductor device110 while in use and cool the overall assembly 100.

In other words, as fluid flows through the plurality of pores 136 and/orother surface features of the MIO bonding structure 130, latent heat ofthe assembly 100 is absorbed by the fluid due to the relative coolertemperature of the fluid. Additionally, with the heat effectivelyabsorbed by the fluid received through the porous structure of the MIObonding structure 130, the heat is transferred through the MIO bondingstructure 130 with the movement of the fluid to other portions of theassembly 100 to draw the heat away from the one or more heat generatingdevices (i.e., the semiconductor device 110). In some embodiments, heatcan be transferred to the fluid from the MIO bonding structure 130 suchthat the fluid carries the heat away from the semiconductor device 110.While the plurality of pores 136 of the present example are specificallyshown and described herein as defining a series of dimples 138throughout the MIO bonding structure 130, other surface featurescontained within the MIO bonding structure 130 may also be includedwithout departing from the scope of the present disclosure.

The number of pores 136 and/or other surface features present in the MIObonding structure 130 is not limited by the present disclosure, and maybe any number so long as the connectivity between the material of theMIO bonding structure 130 and the top surface 122 of the substrate 120and the bottom surface 114 of the semiconductor device 110 ismaintained. While the plurality of pores 136 are depicted as beinggenerally spherical in shape, this is merely illustrative. Accordingly,it should be understood that the plurality of pores 136 may be anyshape, including, for example, spherical, cylindrical, and/or irregularshapes. The shape of the pores 136 may be determined from the shape ofthe materials used to form the MIO bonding structure 130 (i.e., the typeof metal). Further, the thickness of the MIO bonding structure 130 isnot limited by the present disclosure, and may generally be anythickness.

As briefly described above, the MIO bonding structure 130 may generallybe constructed of a thermally conductive material, but is otherwise notlimited by the present disclosure. In some embodiments, the materialused for the MIO bonding structure 130 may be selected based on theprocess used to form the MIO bonding structure 130, as described ingreater detail herein. For example, if the MIO bonding structure 130 isformed from an MIO formation process, metals that are suitable for sucha formation process may be used. Illustrative examples of materials thatmay be used include, but are not limited to, aluminum, nickel, copper,silver, gold, an alloy containing any of the foregoing, a compoundcontaining any of the foregoing, and the like. Other materials that aregenerally understood to result from an inverse opal formation processthat are not specifically disclosed herein are also included within thescope of the present disclosure.

It should be understood that inverse opal structures (including MIOstructures) have a high permeability, as inverse opal wick structuresprovide the advantage of improved control over pore sizes anddistribution. Accordingly, the thermal conductivity of the MIO bondingstructure 130 can be varied and controlled to accommodatethermomechanical stresses generated within the assembly 100. In someembodiments, the MIO bonding structure 130 is further configured toprovide heat flux thermal management within the assembly 100 such thatthe MIO bonding structure 130 may improve heat exchange between thesemiconductor device 110 and the substrate 120 at a high heat removalrate. It should be understood that in other embodiments, the assembly100 may include other arrangements and/or configurations than that shownand described above, as described herein below.

Referring now to FIGS. 2A-2D and the flow chart of FIG. 4, an examplemethod 200 for forming the assembly 100 with the opal structure 140generally described above is shown. It should be understood that method200 is merely illustrative and that the assembly 100 may be formed viaother methods. At block 202, and as depicted in FIG. 2A, the substrate120 is positioned against the opal structure 140, and in particular, thetop surface 122 of the substrate 120 is disposed on the second majorsurface 144 of the opal structure 140. In some embodiments, thesubstrate 120 is electrodeposited onto the opal structure 140. It shouldbe understood that in other embodiments, the substrate 120 may bedeposited on the second major surface 144 of the opal structure 140after positioning a plurality of polymer spheres 150 against the firstmajor surface 142 of the opal structure 140.

At block 204, and as depicted in FIG. 2B, the plurality of polymerspheres 150 are positioned on and against the opal structure 140opposite of the substrate 120. In particular, the first major surface142 of the opal structure 140 is positioned against the bottom surface154 of the plurality of polymer spheres 150. In this instance, theplurality of polymer spheres 150 and the opal structure 140 are notbonded together by an intermediary bonding layer disposed therebetween.However, it should be understood that the opal structure 140 and theplurality of polymer spheres 150 may be bonded together with anintermetallic compound layer formed therebetween in other embodiments.It should further be understood that in some embodiments the pluralityof polymer spheres 150 may initially be deposited on the semiconductordevice 110 (FIG. 2D), and in particular along the bottom surface 114,prior to being deposited along the first major surface 142 of the opalstructure 140. In this instance, the semiconductor device 110 and theplurality of polymer spheres 150 are electroplated and/orelectrolytically deposited onto the opal structure 140.

In some embodiments, the opal structure 140 includes a plurality ofspheres 148 (e.g., polymer spheres) extending between the first majorsurface 142 and the second major surface 144 and forming a plurality ofvoids 146 disposed between the plurality of spheres 148. It should beunderstood that several methods of constructing the opal structure 140are possible. One illustrative method to synthesize the opal structure140 is via a controlled withdrawal process whereby a colloidalsuspension of spheres 148 is provided via a tube, a substrate isinserted into the suspension in order to create a meniscus line withinthe tube, and the suspending agent (e.g., water) is slowly evaporated.The surface tension of the evaporating suspending agent at the top ofthe meniscus line pulls the spheres 148 into a closely packed array nomore than a few layers thick, leaving the opal structure 140 of spheres148 within the tube. This opal structure 140 of spheres 148, as depictedin FIGS. 2A-2B, is arranged such that a plurality of voids 146 arepresent around each of the spheres 148 of the opal structure 140. Theopal structure 140 is generally constructed of a material that can laterbe dissolved, etched, or otherwise removed without altering the shape ofthe spheres 148, voids 146, and/or other surface features, as describedherein. For example, in some embodiments the material of the opalstructure 140 may be a polymer. In some embodiments, the opal structure140 may be a self-assembled patterned structure.

As particularly depicted in FIGS. 2A-2B, the plurality of spheres 148are positioned throughout the opal structure 140 to form aninterconnected network of voids 146 throughout the opal structure 140.The plurality of spheres 148 are arranged to receive a material withinthe plurality of voids 146, such as, for example, a metal, to form theMIO bonding structure 130. As will be described in greater detailherein, the plurality of polymer spheres 150 may be disposed within theplurality of voids 146 of the opal structure 140, may extend along thesides and/or an exterior of the opal structure 140, and/or the like. Theplurality of polymer spheres 150 includes a solder material (i.e., abonding material) disposed therein, respectively, and in particular eachpolymer sphere 150 of the plurality of polymer spheres 150 includes asolder sphere 156 disposed between a top surface 152 of the polymersphere 150 and a bottom surface 154 of the polymer sphere 150. Theplurality of solder spheres 156 may be formed of a bonding material,such as, for example, tin. Accordingly, it should be understood that thesolder sphere 156 formed of a solder bonding material, such as, forexample, tin, is encapsulated within each of the polymer spheres 150 ofthe plurality of polymer spheres 150.

At block 206, with the substrate 120 secured against the opal structure140 and the plurality of polymer spheres 150 disposed over the opalstructure 140 opposite of the substrate 120, a material may be depositedon the opal structure 140. In particular, a metal may beelectrolytically or electrolessly deposited onto the opal structure 140.In this instance, the metal is received in and transferred through thestructure of the opal structure 140 via one or more surfaces of the opalstructure 140 except for the second major surface 134 secured to the topsurface 122 of the substrate 120 (e.g., first major surface 132, a sidesurface, and the like). Accordingly, the metal is received along theplurality of spheres 148 such that the metal fills the voids 146 aroundthe spheres 148 of the opal structure 140. The metal may be formed fromany electrically conductive material, such as, for example, copper (Cu),aluminum (Al), nickel (Ni), iron (Fe), zinc (Zn), alloys thereof, andthe like. As used herein, the term “alloys thereof” refers to alloys notlimited to the elements listed unless otherwise stated. For example, aCu alloy as disclosed herein may include an alloy formed from Cu andelements other than Al, Ni, Fe, and Zn. In the alternative, a Cu alloyas disclosed herein may include an alloy formed from Cu with Al, Ni, Feand/or Zn, plus additional elements. In another alternative, a Cu alloyas disclosed herein may include an alloy formed from only Cu and Al, Ni,Fe and/or Zn plus any incidental impurities present from manufacturingof the Cu alloy. It should be understood that the metal that isdeposited is generally the material that results in the MIO bondingstructure 130 (FIG. 1) described herein.

The metal may be deposited via any generally recognized method ofdeposition, such as, for example, chemical vapor deposition (CVD),electrodeposition, epitaxy, and thermal oxidation. In some embodiments,physical vapor deposition (PVD) or casting may also be used to depositthe metal. It should be understood that the deposition process does notcompletely fill the interstitial spaces (e.g., the plurality of voids146), but rather creates a layer of material around the plurality ofspheres 148 such that, when removed, the plurality of pores 136, theplurality of dimples 138, and/or other surface features of the MIObonding structure 130 (FIG. 1) are formed.

At block 208, the opal structure 140 is removed from between thesubstrate 120 and the plurality of polymer spheres 150 to form apatterned structure therein, and in particular, the MIO bondingstructure 130 within the assembly 100. In other words, with the metalreceived within the plurality of voids 146 and around the plurality ofspheres 148 of the opal structure 140, metal inverse opals areeffectively formed on the substrate 120, and in particular, along thetop surface 122 of the substrate 120 where the opal structure 140engages the substrate 120. Removal of the opal structure 140 maygenerally be completed via any removal processes, particularly removalprocesses that are suitable for removing the material used for the opalstructure 140 (e.g., a polymer) but not the metal received therein. Forexample, an etching process may be used to remove the opal structure140. That is, an etchant (i.e., solution) may be applied to the opalstructure 140 (e.g., by placing the opal structure 140 in an etchantbath) to etch away the opal structure 140. In some embodiments, ahydrofluoric acid solution may be used as an etchant to etch away theopal structure 140. Other methods that cause the opal structure 140 tobe removed or otherwise dissolved should generally be understood. As aresult of this process, the MIO bonding structure 130 is formed on thetop surface 122 of the substrate 120. Other methods that cause the opalstructure 140 to be removed or otherwise dissolved should generally beunderstood.

Referring now to FIG. 2C, the MIO bonding structure 130 is disposedbetween and bonded to the substrate 120 and the plurality of polymerspheres 150. In particular, the first major surface 142 of the opalstructure 140 is effectively the first major surface 132 of the MIObonding structure 130 such that the first major surface 132 is bonded tothe top surface 122 of the substrate 120. The second major surface 144of the opal structure 140 is the second major surface 134 of the MIObonding structure 130, upon removal of the opal structure 140, such thatthe second major surface 134 is bonded to the bottom surface 154 of theplurality of polymer spheres 150. It should be understood that in otherembodiments the plurality of polymer spheres 150 may be deposited ontothe MIO bonding structure 130, and in particular the first major surface132, after the opal structure 140 is removed.

At block 210, the plurality of polymer spheres 150 are removed from theassembly 100 to expose the bonding/solder material encapsulated therein,and in particular, the plurality of solder spheres 156 encapsulatedwithin the plurality of polymer spheres 150. It should be understoodthat the plurality of polymer spheres 150 may be removed from theassembly 100 via various methods, including, but not limited to,dissolving the plurality of polymer spheres 150 with a solution (e.g., ahydrofluoric acid solution) to thereby uncover the solder sphere 156(FIG. 2C) encapsulated within each of the plurality of polymer spheres150. Although in the present example the plurality of polymer spheres150 are described as being removed after a removal of the opal structure140, it should be understood that in other embodiments the plurality ofpolymer spheres 150 may be removed from the assembly 100 before and/orsimultaneously with the opal structure 140. It should further beunderstood that in some embodiments both the opal structure 140 and theplurality of polymer spheres 150 may be dissolved with the same solution(e.g., a hydrofluoric acid solution). In this instance, the plurality ofsolder spheres 156 are disposed along the first major surface 132 of theMIO bonding structure 130 such that the plurality of solder spheres 156are secured to the MIO bonding structure 130 along a surface of the MIObonding structure 130 opposite of the substrate 120.

At block 212, and as particularly depicted in FIG. 2D, the semiconductordevice 110 may be placed on the MIO bonding structure 130. For instance,the bottom surface 114 of the semiconductor device 110 may be depositedonto the first major surface 132 of the MIO bonding structure 130adjacent to the plurality of solder spheres 156. In particular, thebottom surface 114 of the semiconductor device 110 is positioned incontact with the plurality of solder spheres 156 extending along thefirst major surface 132 of the MIO bonding structure 130. It shouldfurther be understood that the plurality of solder spheres 156 (and/orthe plurality of polymer spheres 150 prior to removal) may be positionedalong various other surfaces of the MIO bonding structure 130, thesemiconductor device 110, and/or the substrate 120 to effectively bondthe semiconductor device 110 to the substrate 120.

At block 214, the semiconductor device 110 may be bonded to the MIObonding structure 130 via electroplating, thermal bonding, transientliquid phase (TLP) bonding, electrolytic or electroless bonding, and/orthe like. It should be understood that TLP bonding may be particularlyused in instances where the semiconductor device 110 is a wide bandgapsemiconductor device that operates at relatively high temperatures(e.g., at a temperature of about 200° Celsius or greater than about 200°Celsius). This is particularly due to the TLP bond layers being capableof adhering the components of the assembly 100 (i.e., the semiconductordevice 110, the MIO bonding structure 130, and/or the substrate 120) atrelatively high temperatures better than other layers, such as, forexample, a solder layer. It should further be understood that, with thebottom surface 114 of the semiconductor device 110 in contact with theplurality of solder spheres 156 prior to TLP bonding, the plurality ofsolder spheres 156 are effectively melted during bonding of the assembly100, thereby adhering the semiconductor device 110 to the first majorsurface 132 of the MIO bonding structure 130 (FIG. 1).

Referring now to FIG. 2E, the plurality of solder spheres 156 are meltedduring TLP bonding of the assembly 100 such that a solder material 159forming the solder spheres 156 are effectively wicked into andtransferred through the plurality of pores 136 of the MIO bondingstructure 130, via a capillary action, to adhere the semiconductordevice 110 to the MIO bonding structure 130. In particular, thesemiconductor device 110 is bonded to the MIO bonding structure 130along the interface extending between the bottom surface 114 of thesemiconductor device 110 and the first major surface 132 of the MIObonding structure 130 where the plurality of solder spheres 156 arepositioned. In other words, bonding the assembly 100 causes theplurality of solder spheres 156 to melt between the semiconductor device110 and the MIO bonding structure 130, which promotes an adhesion of thesemiconductor device 110 to the MIO bonding structure 130. To melt theplurality of solder spheres 156, the assembly 100 is heated during TLPbonding to a predetermined temperature that exceeds a meltingtemperature of the solder material 159 forming the plurality of solderspheres 156.

In the present example, with the plurality of solder spheres 156 formedof tin (i.e., the solder material 159), a melting temperature of theplurality of solder spheres 156 is approximately 230° Celsius such thatthe assembly 100 is heated to a predetermined temperature greater thanat least 230° Celsius during TLP bonding to effectively melt theplurality of solder spheres 156. It should be understood that inresponse to the plurality of solder spheres 156 melting, the soldermaterial 159 forming the solder spheres 156 (e.g., tin) adheres to thebottom surface 114 of the semiconductor device 110 while being wickedinto (i.e., extend through) a portion of the plurality of pores 136 ofthe MIO bonding structure 130 (FIG. 2E). Accordingly, as a portion ofthe tin (i.e., the solder material 159) from the plurality of solderspheres 156 contacts the bottom surface 114 of the semiconductor device110 and a remaining portion of the tin passes through the plurality ofpores 136 of the MIO bonding structure 130, the semiconductor device 110is effectively bonded to the MIO bonding structure 130 upon a cooling ofthe assembly 100. In other words, with the tin from the plurality ofsolder spheres 156 received in and integrated through the plurality ofpores 136 while in contact with the bottom surface 114 of thesemiconductor device 110, a cooling of the tin results in a phase changethat provides for the semiconductor device 110 bonding to the MIObonding structure 130.

It should be understood that the tin from the plurality of solderspheres 156 may extend partially or entirely through a thickness of theMIO bonding structure 130 dependent on various factors, including butnot limited to, a quantity of the plurality of solder spheres 156positioned within the assembly 100. For instance, in the presentexample, the tin from the plurality of solder spheres 156 is depicted aspartially extending into the MIO bonding structure 130 (FIG. 2E) as aresult of the number of the plurality of polymer spheres 150 initiallydeposited in the assembly 100, and the corresponding number of solderspheres 156 encapsulated within the plurality of polymer spheres 150(FIG. 2D). In other embodiments, additional and/or fewer polymer spheres150 and/or solder spheres 156 may be included in the assembly 100, andin particular deposited along the MIO bonding structure 130, to providea greater or lesser quantity of tin extending through the plurality ofpores 136 of the MIO bonding structure 130, respectively, in response tomelting the plurality of solder spheres 156 during a bonding process ofthe assembly 100. Additional polymer spheres 150 may be positioned alongthe first major surface 132, the second major surface 134, and/or alongone or more side surfaces of the MIO bonding structure 130 to provide agreater amount of tin received within the MIO bonding structure 130 whenbonding the assembly 100 at elevated temperatures, thereby causing theplurality of solder spheres 156 (e.g., tin spheres) to melt and bewicked into the plurality of pores 136.

It should be understood that in some embodiments an intermetalliccompound layer and/or bond may be formed between the semiconductordevice 110 and the MIO bonding structure 130 along the interface of thebottom surface 114 and the first major surface 132 in response to theplurality of solder spheres 156 melting during the TLP bonding. Itshould also be understood that in some embodiments, dependent on alocation of the plurality of solder spheres 156, melting the pluralityof solder spheres 156 may facilitate an adhesion of the substrate 120 tothe MIO bonding structure 130. In response to the plurality of solderspheres 156 melting and joining the semiconductor device 110 to the MIObonding structure 130 and/or the substrate 120 to the MIO bondingstructure 130, the assembly 100 is formed as a result.

Referring now to FIGS. 4A-4B, a non-limiting example of an assembly 300,such as, for example, a power electronics assembly is illustrated. Inthe example shown, it should be understood that the assembly 300 issubstantially similar to the assembly 100 described above such that likereference numerals are used to identify like components. An examplemethod of forming the assembly 300 with the opal structure 140 may bedifferent than the example method 200 shown and described above asexplicitly noted herein. For instance, referring to the flow chart ofFIG. 5, an example method 400 for forming the assembly 300 is shown. Itshould be understood that method 400 is merely illustrative and that theassembly 300 may be formed via other methods.

Referring to FIGS. 4A and 5, at block 402, the substrate 120 ispositioned against the opal structure 140, and in particular, the topsurface 122 of the substrate 120 is disposed along the second majorsurface 144 of the opal structure 140. At block 404, a material (e.g., ametal) may be received within the opal structure 140, and in particular,deposited into the plurality of voids 146 of the opal structure 140 asdescribed in greater detail above. At block 406, the semiconductordevice 110 may be placed on the opal structure 140, and in particular,the bottom surface 114 of the semiconductor device 110 may be depositedonto the first major surface 142 of the opal structure 140. In thisexample, the semiconductor device 110 is deposited onto the first majorsurface 142 of the opal structure 140 prior to positioning a solderpaste 160 on the opal structure 140.

Referring to FIGS. 4B and 5, at block 408, the opal structure 140 isremoved to thereby form the MIO bonding structure 130 of the assembly300. It should be understood that the opal structure 140 may be removedfrom the assembly 300 via various methods, including those described ingreater detail above with respect to assembly 100. At block 410, and asparticularly depicted in FIG. 4B, the solder paste 160 is positionedalong the sides of the MIO bonding structure 130, and in particular,along an exterior periphery surface of the MIO bonding structure 130extending between the first major surface 132 and the second majorsurface 134. In the present example, the solder paste 160 extends alongan outer lateral surface 139 of the MIO bonding structure 130 ratherthan along the first major surface 132 of the MIO bonding structure 130as described above with respect to the assembly 100 and shown in FIGS.1-2. It should be understood that the solder paste 160 may extend alongadditional and/or fewer surfaces or sides of the MIO bonding structure130 than those shown and described herein. It should also be understoodthat in some embodiments the solder paste 160 may be positioned along anexterior periphery surface of the opal structure 140, between the firstmajor surface 142 and the second major surface 144, prior to adissolution of the opal structure 140.

Unlike the method 200 described and shown above, which included thesolder spheres 156 formed of solder material 159 that is encapsulatedwithin the plurality of polymer spheres 150, in the present examplemethod 400 the solder paste 160 of the assembly 300 is already exposedsuch that a dissolution to expose the solder material of the solderpaste 160 is not required in the present example. Accordingly, it shouldbe understood that the solder paste 160 of the present example isalready positioned along the MIO bonding structure 130 and adjacent tothe bottom surface 114 of the semiconductor device 110 such that anadditional process of exposing a solder material (e.g., tin) of thesolder paste 160 is not necessary in the example method 400 shown anddescribed herein.

Referring to FIG. 5, at block 412, the semiconductor device 110 may bebonded to the MIO bonding structure 130 via electroplating, thermalbonding, transient liquid phase (TLP) bonding, electrolytic orelectroless bonding, and/or the like. In this instance, the solder paste160 is melted and wicked into (i.e., transferred through) the pluralityof pores 136 of the MIO bonding structure 130 during the bonding process(e.g., TLP bonding) due to the position of the solder paste 160 alongthe sides of the MIO bonding structure 130 to adhere the semiconductordevice 110 to the MIO bonding structure 130 along the interfaceextending between the bottom surface 114 of the semiconductor device 110and the first major surface 132 of the MIO bonding structure 130. Asdescribed in greater detail above with respect to the assembly 100 andmethod 200, bonding the assembly 300 causes the solder paste 160 tomelt, which promotes an adhesion of the semiconductor device 110 to theMIO bonding structure 130 thereby forming the assembly 300. In thepresent example, the inclusion of the solder paste 160 along multipleouter, side surfaces 139 of the MIO bonding structure 130 promotesadhesion of the semiconductor device 110 to the MIO bonding structure130 by extracting the material that the solder paste 160 is formed of(e.g., tin) into the plurality of pores 136 of the MIO bonding structure130 via a capillary action and thereby exposing the semiconductor device110 to the solder material (e.g., tin) along the bottom surface 114during the bonding process. In other words, as the solder paste 160melts the material of the solder paste 160 is drawn into the pluralityof pores 136 of the MIO bonding structure 130 via a capillary action,which further contacts the bottom surface 114 of the semiconductordevice 110 due to the semiconductor device 110 being deposited along thefirst major surface 132 of the MIO bonding structure 130. With thematerial of the solder paste 160 (e.g., tin) received in and integratedthrough the plurality of pores 136 while in contact with the bottomsurface 114 of the semiconductor device 110, a cooling of the tinresults in a phase change that provides for the semiconductor device 110bonding to the MIO bonding structure 130.

Referring now to FIGS. 6A-6B, a non-limiting example of an assembly 500,such as, for example, a power electronics assembly is illustrated. Inthe example shown, it should be understood that the assembly 500 issubstantially similar to the assembly 100 described above such that likereference numerals are used to identify like components. Rather, anexample method of forming the assembly 500 with the opal structure 140may be different than the example method 200 shown and described above.For instance, referring to the flow chart of FIG. 7, an example method600 for forming the assembly 500 is shown. It should be understood thatmethod 600 is merely illustrative and that the assembly 500 may beformed via other methods.

Referring to FIGS. 6A and 7, at block 602, the substrate 120 ispositioned against the opal structure 140, and in particular, the topsurface 122 of the substrate 120 is disposed along the second majorsurface 144 of the opal structure 140. At block 604, and as particularlydepicted in FIG. 6A, the plurality of polymer spheres 150 are positionedwithin the opal structure 140 rather than along the first major surface142 of the opal structure 140 as described above with respect to theassembly 100 and shown in FIGS. 1-2 and/or along a periphery of the opalstructure 140 as described above with respect to assembly 300 and shownin FIGS. 4A-4B. In particular, the plurality of polymer spheres 150 arepositioned in the plurality of voids 146 of the opal structure 140 suchthat the plurality of polymer spheres 150 are disposed between the firstmajor surface 142 and the second major surface 144 of the opal structure140. It should be understood that the plurality of polymer spheres 150may be dispersed throughout the porous structure of the opal structure140 such that the plurality of solder spheres 156 encapsulated withinthe plurality of polymer spheres 150 are evenly and/or randomlydistributed throughout the plurality of voids 146. It should beunderstood that the plurality of polymer spheres 150 may be positionedalong additional and/or fewer areas and/or surfaces of the opalstructure 140 than those shown and described herein. For example, thepolymer spheres may be in the form of a continuous, thin layer extendingthrough the opal structure 140, rather than in the form of a pluralityof spheres as shown and described herein. In this instance, it should beunderstood that the polymer layer still encapsulates a solder materialtherein (e.g., tin) and may extend through a longitudinal length of theopal structure 140 along various sizes, shapes, and/or configurationswithout departing from the scope of the present disclosure.

At block 606, a material (e.g., a metal) may be received within the opalstructure 140, and in particular, deposited into the plurality of voids146 of the opal structure 140 as described in greater detail above. Itshould be understood that a portion of the material may be receivedwithin the plurality of voids 146 of the opal structure 140 that do notinclude the plurality of polymer spheres 150 therein. At block 608, thesemiconductor device 110 may be placed on the opal structure 140, and inparticular, the bottom surface 114 of the semiconductor device 110 maybe deposited onto the first major surface 142 of the opal structure(FIG. 6A). In this example, the semiconductor device 110 is depositedonto the first major surface 142 of the opal structure 140 afterpositioning the plurality of polymer spheres 150 within opal structure140. It should be understood that in other embodiments the semiconductordevice 110 may be deposited onto the opal structure 140 prior todepositing the plurality of polymer spheres 150 within the plurality ofvoids 146 of the opal structure 140. It should also be understood thatin some embodiments the plurality of polymer spheres 150 may be receivedwithin the opal structure 140 after the semiconductor device 110 isdeposited onto the opal structure 140.

Referring to FIGS. 6B and 7, at block 610, the opal structure 140 isremoved to thereby form the MIO bonding structure 130 of the assembly500. It should be understood that the opal structure 140 may be removedfrom the assembly 500 via various methods, including those described ingreater detail above with respect to assembly 100. At block 612, theplurality of polymer spheres 150 are removed from the assembly 500 toexpose the plurality of solder spheres 156 encapsulated therein. Itshould be understood that the plurality of polymer spheres 150 may beremoved from the assembly 500 via various methods, including thosedescribed in greater above, such as by a solution (e.g., hydrofluoricacid solution). In the present example, with the plurality of polymerspheres 150 deposited within the plurality of voids 146 of the opalstructure 140, dissolving the plurality of polymer spheres 150 afterremoving the opal structure 140 thereby forms the plurality of solderspheres 156 within the plurality of pores 136 of the MIO bondingstructure 130, as depicted in FIG. 6B. In other words, upon removing theopal structure 140 and the plurality of polymer spheres 150 inaccordance with the steps described above and shown herein, theplurality of solder spheres 156 formed in response to removing theplurality of polymer spheres 150 are exposed and positioned within theplurality of pores 136 of the MIO bonding structure 130 (as formed inresponse to removing the opal structure 140).

It should be understood that the plurality of solder spheres 156 may bedispersed throughout the porous structure of the MIO bonding structure130 such that the plurality of solder spheres 156 are evenly and/orrandomly distributed throughout the plurality of pores 136. In thepresent example, the inclusion and distribution of the plurality ofsolder spheres 156 within multiple pores 136 of the MIO bondingstructure 130 serves to promote adhesion of the semiconductor device 110to the MIO bonding structure 130 by contacting a greater surface area ofthe bottom surface 114 of the semiconductor device 110 to the firstmajor surface 132 of the MIO bonding structure 130 when the plurality ofsolder spheres 156 are melted during a bonding process of the assembly500. Additionally, in some embodiments the plurality of polymer spheres150 may further extend along the first major surface 142 of the opalstructure 140, in addition to being received within the plurality ofvoids 146, such that removing the plurality of polymer spheres 150 formsthe plurality of solder spheres 156 throughout the MIO bonding structure130 and along the first major surface 132. It should be understood thatthe plurality of polymer spheres 150 may be received within apredetermined set of the plurality of voids 146 of the opal structure140 such that the plurality of solder spheres 156 are formed in acorresponding, predetermined pattern throughout the network of theplurality of pores 136 of the MIO bonding structure 130.

As further seen in FIG. 6B, the plurality of solder spheres 156 aredeposited in proximate contact with the semiconductor device 110 and indirect contact with the MIO bonding structure 130. Although theplurality of solder spheres 156 of the assembly 500 are described hereinin the present example method 600 as being formed after removing theopal structure 140 to form the MIO bonding structure 130, it should beunderstood that in some embodiments the plurality of polymer spheres 150may be removed before and/or simultaneously with a removal of the opalstructure 140.

Referring to FIGS. 6B and 7, at block 614, the semiconductor device 110may be bonded to the MIO bonding structure 130 via electroplating,thermal bonding, transient liquid phase (TLP) bonding, electrolytic orelectroless bonding, and/or the like. In this instance, the plurality ofsolder spheres 156 are melted from within the plurality of pores 136 ofthe MIO bonding structure 130 during the bonding process (e.g., TLPbonding) due to the position of the plurality of solder spheres 156.With the semiconductor device 110 positioned against the first majorsurface 132 of the MIO bonding structure 130 in close proximity to theplurality of pores 136, the material composing the plurality of solderspheres 156 (e.g., tin) serves to adhere the semiconductor device 110 tothe MIO bonding structure 130 along the interface extending between thebottom surface 114 of the semiconductor device 110 and the first majorsurface 132 of the MIO bonding structure 130 during a bonding of theassembly 500. As described in greater detail above with respect to theassembly 100 and method 200, bonding the assembly 500 causes theplurality of solder spheres 156 to melt, which promotes an adhesion ofthe semiconductor device 110 to the MIO bonding structure 130 therebyforming the assembly 500. In the present example, the distribution ofthe plurality of solder spheres 156 throughout the porous structure ofthe MIO bonding structure 130 promotes adhesion of the semiconductordevice 110 to the MIO bonding structure 130 by exposing a greatersurface area of the semiconductor device 110 to the material of thesolder spheres 156 (e.g., tin) received within the MIO bonding structure130 during the bonding process.

It should now be understood that the methods for fabricating a powerelectronic assembly, and in particular bonding a semiconductor device toa metal substrate with a metal inverse opal structure disposedtherebetween, may be utilized to bond the components of an assemblytogether without the need for additional interface and/or bonding layersin the resulting assembly structure. In particular, the integration ofone or more solder spheres encapsulated within a dissolvable, polymersphere in the fabrication method described herein may provide asimplified process for securing assembly components to a porousinterlayer (e.g., an MIO bonding structure) that includes a plurality ofpores/voids capable of reducing thermally induced stresses of theassembly during operation.

It is noted that the term “about” and “generally” may be utilized hereinto represent the inherent degree of uncertainty that may be attributedto any quantitative comparison, value, measurement, or otherrepresentation. This term is also utilized herein to represent thedegree by which a quantitative representation may vary from a statedreference without resulting in a change in the basic function of thesubject matter at issue. The terms “top”, “bottom” and “middle” are usedin relation to the figures and are not meant to define an exactorientation of power electronics assemblies or layers used to form powerelectronic assemblies described herein.

While particular embodiments have been illustrated and described herein,it should be understood that various other changes and modifications maybe made without departing from the spirit and scope of the claimedsubject matter. Moreover, although various aspects of the claimedsubject matter have been described herein, such aspects need not beutilized in combination. It is therefore intended that the appendedclaims cover all such changes and modifications that are within thescope of the claimed subject matter.

What is claimed is:
 1. A method of forming a bonding assembly, themethod comprising: positioning a plurality of polymer spheres against anopal structure, the opal structure comprising a first major surface anda second major surface with a plurality of voids defined therebetween,wherein each of the plurality of polymer spheres encapsulates a soldermaterial disposed therein and contacts the first major surface of theopal structure; placing a substrate against the second major surface ofthe opal structure; depositing a material within the voids of the opalstructure; removing the opal structure to form an inverse opal structurebetween the first and second major surfaces; removing the plurality ofpolymer spheres to expose the solder material encapsulated therein; andplacing a semiconductor device onto the inverse opal structure incontact with the solder material.
 2. The method of claim 1, whereinremoving the plurality of polymer spheres and the opal structurecomprises dissolving the plurality of polymer spheres and the opalstructure with a solution.
 3. The method of claim 2, wherein thesolution is a hydrofluoric acid solution.
 4. The method of claim 2,wherein dissolving the opal structure with the solution causes aplurality of dimples and a plurality of pores to form the inverse opalstructure.
 5. The method of claim 1, wherein the plurality of polymerspheres is positioned against the opal structure after disposing thesubstrate against the opal structure.
 6. The method of claim 1, whereindisposing the substrate against the opal structure compriseselectrodepositing the substrate onto the opal structure.
 7. The methodof claim 1, further comprising bonding the semiconductor device to theinverse opal structure by melting the solder material disposedtherebetween.
 8. The method of claim 1, wherein the material comprises ametal.
 9. The method of claim 1, wherein the solder materialencapsulated within the plurality of polymer spheres is formed of abonding material that is different than the plurality of polymerspheres.
 10. The method of claim 9, wherein the bonding materialcomprises tin.
 11. The method of claim 1, further comprising positioningthe plurality of polymer spheres around an outer surface of the inverseopal structure.
 12. The method of claim 1, further comprisingpositioning the plurality of polymer spheres around an outer surface ofthe opal structure after depositing the semiconductor device onto theopal structure.
 13. The method of claim 1, further comprising disposingthe plurality of polymer spheres within the plurality of voids of theopal structure.
 14. The method of claim 13, wherein removing the opalstructure and the plurality of polymer spheres comprises forming theinverse opal structure with the solder material disposed therein.
 15. Amethod of forming a power electronic assembly comprising: attaching ametal substrate to a first surface of an opal structure, the opalstructure comprising a plurality of voids defined between the firstsurface and a second surface; attaching a plurality of polymer spheresto the second surface of the opal structure, the plurality of polymerspheres encapsulating a solder material disposed therein; forming aninverse opal structure between the metal substrate and the plurality ofpolymer spheres by removing the opal structure disposed therebetween;exposing the solder material from within the plurality of polymerspheres by removing the plurality of polymer spheres; and securing anon-metal substrate against the inverse opal structure and in contactwith the solder material.
 16. The method of claim 15, attaching thenon-metal substrate to the inverse opal structure by melting the soldermaterial disposed therebetween.
 17. The method of claim 16, wherein thesolder material encapsulated within the plurality of polymer spheres isformed of tin such that melting the solder material comprises liquefyingtin between the non-metal substrate and the inverse opal structure. 18.A method for bonding a semiconductor device to a substrate using metalinverse opals, the method comprising: depositing the substrate onto afirst major surface of an opal structure, the opal structure defining aplurality of voids between the first major surface and a second majorsurface of the opal structure; receiving a plurality of polymer sphereswithin at least one of the plurality of voids of the opal structure;electrodepositing metal within the plurality of voids of the opalstructure to bond the substrate to the opal structure; dissolving theopal structure to provide a metal inverse opal structure secured alongthe substrate, the metal inverse opal structure defining a plurality ofspheres; and dissolving the plurality of polymer spheres from within themetal inverse opal structure to expose an encapsulated materialpositioned within the plurality of polymer spheres; and depositing thesemiconductor device onto the metal inverse opal structure to bond thesubstrate to the semiconductor device.
 19. The method of claim 18,further comprising melting the encapsulated material from within theplurality of spheres of the metal inverse opal structure to secure thesemiconductor device to the substrate.
 20. The method of claim 18,wherein the encapsulated material comprises tin.